FM Modulation Signal Circuit With Temperature Drift Compensation
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Solution Overview
Problem
The existing modulation-signal generating circuits in radar devices face challenges in achieving high linearity and precision due to temperature variations, requiring extensive testing and adjustments for each manufacturing lot and process, leading to increased production costs and time.
Innovation Solution
A modulation-signal generating circuit with a temperature monitoring unit, a voltage control oscillator having two variable impedance circuits, and a frequency-correction-voltage generating unit that outputs a temperature-independent DC component and AC component, allowing for independent temperature compensation of the oscillation frequency, thereby maintaining modulation linearity and reducing the need for frequent adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a VCO is structured to have a low setting of a Q value of a tuning circuit to achieve a predetermined frequency modulation width, then the frequency modulation width is sufficient, but temperature drift of the output frequency becomes large and the V T -f characteristic changes at ambient temperature
Solution Approach 1:
The patent divides the single VCO into two independent VCOs (first VCO and second VCO), each with their own tuning circuits. The first VCO is dedicated to frequency modulation with a low Q value, while the second VCO is dedicated to temperature compensation with a high Q value. This segmentation allows each VCO to optimize its function without compromising the other, resolving the contradiction between achieving sufficient frequency modulation width and maintaining frequency stability against temperature drift.
2Adaptability or versatility
If the operation point is shifted to a horizontal direction at ambient temperature to avoid output frequency exceeding the legal frequency range, then the frequency range compliance is maintained, but the modulation sensitivity changes at different temperatures
Solution Approach 1:
The patent introduces a second VCO as an intermediary device that generates temperature-compensated control voltages to adjust the operation points of the first VCO. This intermediary VCO with high Q value acts as a mediator that compensates for temperature-induced frequency drift, thereby maintaining consistent modulation sensitivity across different temperatures while ensuring frequency range compliance through automatic operation point adjustment.
3Measurement precision
If extensive testing and adjustments are performed for each manufacturing lot and process to achieve high linearity, then the measurement precision is improved, but the production time and cost increase
Solution Approach 1:
The patent implements a self-service mechanism where the second VCO automatically generates temperature-compensated control voltages that adjust the operation points of the first VCO based on real-time temperature conditions. This self-adjusting system eliminates the need for extensive manual testing and adjustments for each manufacturing lot, as the circuit automatically compensates for temperature variations during operation, thereby maintaining high measurement precision while significantly reducing production time and cost.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables temperature compensation of the output frequency independently of frequency modulation, maintaining consistent modulation sensitivity across temperatures, reducing test and adjustment time, and improving measurement precision in radar devices.
Implementation Method 1
a voltage control oscillator (VCO) 41 that changes an oscillation frequency according to a control voltage
Implementation Method 2
a temperature monitoring unit (4) that detects a temperature of a casing of the circuit
Implementation Method 3
a frequency-correction-voltage generating unit (3) that outputs a voltage for compensating for a temperature drift of the oscillation frequency
Implementation Method 4
voltage control oscillator including an oscillation circuit and two variable impedance circuits either one of which being connected in series with the oscillation circuit, and which independently control oscillation frequency based on an input control voltage
Data Source
Figure 1~2
Figure 3-1~3-2
Figure 3-3
AI summary
A modulation-signal generating circuit obtains a highly linear FM modulation wave within a legal frequency range. The modulation-signal generating circuit simplifies temperature data of a modulation correction voltage to obtain the FM modulation wave high linearity. The modulation-signal generating circuit includes a temperature monitoring unit 4 that detects a casing temperature of the circuit, a voltage control oscillator 1 having two variable impedance circuits that independently control oscillation frequency based on an input control voltage, a frequency-correction-voltage generating unit 3 that outputs a voltage for compensating for a temperature drift of an oscillation frequency according to the casing temperature detected by the temperature monitoring unit 4, to one of the variable impedance circuits, and an FM-modulation-voltage generating unit 2 that outputs a modulation voltage containing a constant DC component not depending on temperature and a predetermined AC component, to the other variable impedance circuit, under a temperature drift compensation condition of the frequency-correction-voltage generating unit 3.